Augmented levels of CD44 in macrophages from atherosclerotic subjects: a possible IL-6-CD44 feedback loop?

The Role of Macrophages in Atherosclerosis: Pathophysiologic Mechanisms and Treatment Considerations

Atherosclerotic diseases are a leading cause of morbidity and mortality worldwide, despite the recent diagnostic and therapeutic advances. A thorough understanding of the pathophysiologic mechanisms is thus essential to improve the care of affected individuals. Macrophages are crucial mediators of the atherosclerotic cascade, but their role has not been fully elucidated. The two main subtypes, tissue-resident and monocyte-derived macrophages, have distinct functions that contribute to atherosclerosis development or regression. Since polarization of macrophages to an M2 phenotype and induction of macrophage autophagy have been demonstrated to be atheroprotective, targeting these pathways could represent an appealing approach. Interestingly, macrophage receptors could act as drug targets, as seen in recent experimental studies. Last but not least, macrophage-membrane-coated carriers have been investigated with encouraging results.

Research progress on the therapeutic effects of nanoparticles loaded with drugs against atherosclerosis

Presently, there are many drugs for the treatment of atherosclerosis (AS), among which lipid-lowering, anti-inflammatory, and antiproliferative drugs have been the most studied. These drugs have been shown to have inhibitory effects on the development of AS. Nanoparticles are suitable for AS treatment research due to their fine-tunable and modifiable properties. Compared with drug monotherapy, experimental results have proven that the effects of nanoparticle-encapsulated drugs are significantly enhanced. In addition to nanoparticles containing a single drug, there have been many studies on collaborative drug treatment, collaborative physical treatment (ultrasound, near-infrared lasers, and external magnetic field), and the integration of diagnosis and treatment. This review provides an introduction to the therapeutic effects of nanoparticles loaded with drugs to treat AS and summarizes their advantages, including increased targeting ability, sustained drug release, improved bioavailability, reduced toxicity, and inhibition of plaque and vascular stenosis.

Duplex Responsive Nanoplatform with Cascade Targeting for Atherosclerosis Photoacoustic Diagnosis and Multichannel Combination Therapy

The culprits of atherosclerosis are endothelial damage, local disorders of lipid metabolism, and progressive inflammation. Early atherosclerosis is typically difficult to diagnose in time due to the lack of obvious symptoms, thus missing the best period of treatment. In this work, a π-conjugated polymer (PMeTPP-MBT) based on 3,6-bis(4-methylthiophen-2-yl)-2,5-bis(2-octyldodecyl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione is designed as a novel photoacoustic contrast agent. On this basis, an intelligent responsive theranostic nanoplatform (PA/ASePSD) combining astaxanthin and SS-31 peptide and loading with PMeTPP-MBT is developed. The high affinity between the dextran shell with the broken endothelial surface VCAM-1 and CD44 confers active targeting of PA/ASePSD to atherosclerotic lesions. High levels of ROS in the acidic plaque microenvironment act as an intelligent cascade switch to achieve controlled release of astaxanthin, SS-31 peptide, and PMeTPP-MBT for non-invasive photoacoustic diagnosis, as well as plaque inhibition mediated by anti-inflammation and multichannel regulation (including ABCA1, ABCG1, CD36, and LOX-1) of lipid metabolism. Both in vitro and in vivo evaluations confirm the impressive anti-atherosclerotic capability and the accurate photoacoustic diagnosis of PA/ASePSD nanoparticles, thus promising a candidate for early-stage atherosclerosis theranostics.

Tuning macrophages for atherosclerosis treatment

Atherosclerosis is a chronic inflammatory vascular disease and a leading cause of death worldwide. Macrophages play an important role in inflammatory responses, cell-cell communications, plaque growth and plaque rupture in atherosclerotic lesions. Here, we review the sources, functions and complex phenotypes of macrophages in the progression of atherosclerosis, and discuss the recent approaches in modulating macrophage phenotype and autophagy for atherosclerosis treatment. We then focus on the drug delivery strategies that target macrophages or use macrophage membrane-coated particles to deliver therapeutics to the lesion sites. These biomaterial-based approaches that target, modulate or engineer macrophages have broad applications for disease therapies and tissue regeneration.

Targeted therapy of atherosclerosis by pH-sensitive hyaluronic acid nanoparticles co-delivering all-trans retinal and rapamycin

Atherosclerosis, the leading cause of death in the elderly worldwide, is typically characterized by elevated reactive oxygen species (ROS) levels and a chronic inflammatory state at the arterial plaques. Herein, pH-sensitive nanoparticles (HR_RAP NPs) co-delivering all-trans retinal (ATR), an antioxidant linked to hyaluronic acid (HA) through a pH-sensitive hydrazone bond, and rapamycin (RAP), an anti-atherosclerotic drug loaded into the nanoparticle core, are developed for targeted combination therapy of atherosclerosis. In this way, HR_RAP NPs might simultaneously reduce ROS levels via ATR antioxidant activity and reduce inflammation via the anti-inflammatory effect of RAP. In response to mildly acidic conditions mimicking the lesional inflammation in vitro, HR_RAP NPs dissociated and both ATR and RAP were effectively released. The developed HR_RAP NPs effectively inhibited pro-inflammatory macrophage proliferation, and displayed dose- and time-dependent specific internalization by different cellular models of atherosclerosis. Also, HR_RAP NP combination therapy showed an efficient synergetic anti-atherosclerotic effect in vitro by effectively inhibiting the inflammatory response and oxidative stress in inflammatory cells. More importantly, HR NPs specifically accumulated in the atherosclerotic plaques of apolipoprotein E-deficient (ApoE^-/-) mice, by active interaction with HA receptors overexpressed by different cells of the plaque. The treatment with HR_RAP NPs remarkably inhibited the progression of atherosclerosis in ApoE^-/- mice which resulted in stable plaques with considerably smaller necrotic cores, lower matrix metalloproteinase-9, and decreased proliferation of macrophages and smooth muscle cells (SMCs). Furthermore, HR_RAP NPs attenuated RAP adverse effects and exhibited a good safety profile after long-term treatment in mice. Consequently, the developed pH-sensitive HR_RAP NP represent a promising nanoplatform for atherosclerosis combination therapy.

Interleukin-6: A Novel Target for Cardio-Cerebrovascular Diseases

Cardio-Cerebrovascular Disease is a collective term for cardiovascular disease and cerebrovascular disease, being a serious threat to human health. A growing number of studies have proved that the content of inflammatory factors or mediators determines the stability of vascular plaque and the incidence of cardio-cerebrovascular event, and involves in the process of Cardio-Cerebrovascular Diseases. Interleukin-6 is a widely used cytokine that causes inflammation and oxidative stress, which would further result in cardiac and cerebral injury. The increased expression of interleukin-6 is closely related to atherosclerosis, myocardial infarction, heart failure and ischemic stroke. It is a key risk factor for these diseases by triggering inflammatory reaction and inducing other molecules release. Therefore, interleukin-6 may become a potential target for Cardio-Cerebrovascular Diseases in the future. This paper is aimed to discuss the expression changes and pathological mechanisms of interleukin-6 in Cardio-Cerebrovascular Diseases, and to provide a novel strategy for the prevention and treatment of Cardio-Cerebrovascular Diseases.

Cardiovascular Effects Mediated by HMMR and CD44

Cardiovascular disease (CVD) is the leading cause of death worldwide. The most dangerous life-threatening symptoms of CVD are myocardial infarction and stroke. The causes of CVD are not entirely clear, and new therapeutic targets are still being sought. One of the factors involved in CVD development among vascular damage and oxidative stress is chronic inflammation. It is known that hyaluronic acid plays an important role in inflammation and is regulated by numerous stimuli, including proinflammatory cytokines. The main receptors for hyaluronic acid are CD44 and RHAMM. These receptors are membrane proteins that differ in structure, but it seems that they can perform similar or synergistic functions in many diseases. Both RHAMM and CD44 are involved in cell migration and wound healing. However, their close association with CVD is not fully understood. In this review, we describe the role of both receptors in CVD.

Effective atherosclerotic plaque inflammation inhibition with targeted drug delivery by hyaluronan conjugated atorvastatin nanoparticles

Atherosclerosis is associated with inflammation in the arteries, which is a major cause of heart attacks and strokes. Reducing the extent of local inflammation at atherosclerotic plaques can be an attractive strategy to combat atherosclerosis. While statins can exhibit direct anti-inflammatory activities, the high dose required for such a therapy renders it unrealistic due to their low systemic bioavailabilities and potential side effects. To overcome this, a new hyaluronan (HA)-atorvastatin (ATV) conjugate was designed with the hydrophobic statin ATV forming the core of the nanoparticle (HA-ATV-NP). The HA on the NPs can selectively bind with CD44, a cell surface receptor overexpressed on cells residing in atherosclerotic plaques and known to play important roles in plaque development. HA-ATV-NPs exhibited significantly higher anti-inflammatory effects on macrophages compared to ATV alone in vitro. Furthermore, when administered in an apolipoprotein E (ApoE)-knockout mouse model of atherosclerosis following a 1-week treatment regimen, HA-ATV-NPs markedly decreased inflammation in advanced atherosclerotic plaques, which were monitored through contrast agent aided magnetic resonance imaging. These results suggest CD44 targeting with HA-ATV-NPs is an attractive strategy to reduce harmful inflammation in atherosclerotic plaques.

Atherosclerosis Treatment with Stimuli-Responsive Nanoagents: Recent Advances and Future Perspectives

Atherosclerosis is the root of approximately one-third of global mortalities. Nanotechnology exhibits splendid prospects to combat atherosclerosis at the molecular level by engineering smart nanoagents with versatile functionalizations. Significant advances in nanoengineering enable nanoagents to autonomously navigate in the bloodstream, escape from biological barriers, and assemble with their nanocohort at the targeted lesion. The assembly of nanoagents with endogenous and exogenous stimuli breaks down their shells, facilitates intracellular delivery, releases their cargo to kill the corrupt cells, and gives imaging reports. All these improvements pave the way toward personalized medicine for atherosclerosis. This review systematically summarizes the recent advances in stimuli-responsive nanoagents for atherosclerosis management and its progress in clinical trials.

The CD44-HA axis and inflammation in atherosclerosis: A temporal perspective

Cardiovascular disease (CVD) due to atherosclerosis is a disease of chronic inflammation at both the systemic and the tissue level. CD44 has previously been implicated in atherosclerosis in both humans and mice. This multi-faceted receptor plays a critical part in the inflammatory response during the onset of CVD, though little is known of CD44's role during the latter stages of the disease. This review focuses on the role of CD44-dependent HA-dependent effects on inflammatory cells in several key processes, from disease initiation throughout the progression of atherosclerosis. Understanding how CD44 and HA regulate inflammation in atherogenesis is key in determining the utility of the CD44-HA axis as a therapeutic target to halt disease and potentially promote disease regression.

Effects of Nanoprobe Morphology on Cellular Binding and Inflammatory Responses: Hyaluronan-Conjugated Magnetic Nanoworms for Magnetic Resonance Imaging of Atherosclerotic Plaques

Atherosclerosis is an inflammatory disease of arterial walls and the rupturing of atherosclerotic plaques is a major cause of heart attack and stroke. Imaging techniques that can enable the detection of atherosclerotic plaques before clinical manifestation are urgently needed. Magnetic resonance imaging (MRI) is a powerful technique to image the morphology of atherosclerotic plaques. In order to better analyze molecular processes in plaques, contrast agents that can selectively bind to plaque receptors will prove invaluable. CD44 is a cell surface protein overexpressed in plaque tissues, the level of which can be correlated with the risks of plaque rupture. Thus, targeting CD44 is an attractive strategy for detection of atherosclerotic plaques. Herein, we report the synthesis of hyaluronan-conjugated iron oxide nanoworms (HA-NWs). A new purification and gel electrophoresis protocol was developed to ensure the complete removal of free HA from HA-NWs. Compared to the more traditional spherical HA-bearing nanoparticles, HA-NWs had an elongated shape, which interacted much stronger with CD44-expressing cells in CD44- and HA-dependent manners. Furthermore, the HA-NWs did not induce much inflammatory response compared to the spherical HA nanoparticles. When assessed in vivo, HA-NWs enabled successful imaging of atherosclerotic plaques in a clinically relevant model of ApoE knockout transgenic mice for noninvasive plaque detection by MRI. Thus, nanoprobe shape engineering can be a useful strategy to significantly enhance their desired biological properties.

CD44 targeting magnetic glyconanoparticles for atherosclerotic plaque imaging

PURPOSE

The cell surface adhesion molecule CD44 plays important roles in the initiation and development of atherosclerotic plaques. We aim to develop nanoparticles that can selectively target CD44 for the non-invasive detection of atherosclerotic plaques by magnetic resonance imaging.

METHODS

Magnetic glyconanoparticles with hyaluronan immobilized on the surface have been prepared. The binding of these nanoparticles with CD44 was evaluated in vitro by enzyme linked immunosorbent assay, flow cytometry and confocal microscopy. In vivo magnetic resonance imaging of plaques was performed on an atherosclerotic rabbit model.

RESULTS

The magnetic glyconanoparticles can selectively bind CD44. In T2* weighted magnetic resonance images acquired in vivo, significant contrast changes in aorta walls were observed with a very low dose of the magnetic nanoparticles, allowing the detection of atherosclerotic plaques. Furthermore, imaging could be performed without significant delay after probe administration. The selectivity of hyaluronan nanoparticles in plaque imaging was established by several control experiments.

CONCLUSIONS

Magnetic nanoparticles bearing surface hyaluronan enabled the imaging of atherosclerotic plaques in vivo by magnetic resonance imaging. The low dose of nanoparticles required, the possibility to image without much delay and the high biocompatibility are the advantages of these nanoparticles as contrast agents for plaque imaging.

Predicting candidate genes based on combined network topological features: a case study in coronary artery disease

Predicting candidate genes using gene expression profiles and unbiased protein-protein interactions (PPI) contributes a lot in deciphering the pathogenesis of complex diseases. Recent studies showed that there are significant disparities in network topological features between non-disease and disease genes in protein-protein interaction settings. Integrated methods could consider their characteristics comprehensively in a biological network. In this study, we introduce a novel computational method, based on combined network topological features, to construct a combined classifier and then use it to predict candidate genes for coronary artery diseases (CAD). As a result, 276 novel candidate genes were predicted and were found to share similar functions to known disease genes. The majority of the candidate genes were cross-validated by other three methods. Our method will be useful in the search for candidate genes of other diseases.

Effect of serum amyloid A1 treatment on global gene expression in THP-1-derived macrophages

OBJECTIVE

To investigate the effect of serum amyloid A1 (SAA1) on global gene expression in macrophages derived from THP-1 monocytes.

MATERIALS AND METHODS

Global genetic expression in THP-1-derived macrophages was determined using Illumina HT-12 microarray chips and the results were validated by real-time PCR. Cytokine levels in cellular supernatant were quantified by ELISA.

RESULTS

In total, 55 genes were upregulated with fold difference greater than two when THP-1-derived macrophages were incubated with SAA1 for 8 h. SAA1 is a strong cytokine inducer with significant upregulation of chemokines CCL1, CCL3, and CCL4 and this was confirmed by both real-time PCR and ELISA quantification. SAA1 also promotes the upregulation of genes involved in phagocytosis, anti-apoptosis, and tissue remodeling.

CONCLUSIONS

SAA1 appears to play an important role during the immune response and in chronic inflammatory diseases through the stimulation of genes involved in cytokine production, phagocytosis, and anti-apoptosis.

NADPH oxidases regulate CD44 and hyaluronic acid expression in thrombin-treated vascular smooth muscle cells and in atherosclerosis

The intracellular signaling events by which NADPH oxidase-generated reactive oxygen species (ROS) modulate vascular smooth muscle cell (VSMC) function and atherogenesis are yet to be entirely elucidated. We previously demonstrated that NADPH oxidase deficiency decreased atherosclerosis in apoE(-/-) mice and identified adhesion protein CD44 as an important ROS-sensitive gene expressed in VSMC and atherosclerotic lesions. Here, we examined the molecular mechanisms by which NADPH oxidase-generated ROS regulate the expression of CD44 and its principal ligand, hyaluronan (HA), and how CD44-HA interaction affects VSMC proliferation and migration and inflammatory gene expression in apoE(-/-) mice aortas. Thrombin-induced CD44 expression is mediated by transcription factor AP-1 in a NADPH oxidase-dependent manner. NADPH oxidase-mediated ROS generation enhanced thrombin-induced HA synthesis, and hyaluronan synthase 2 expression in VSMC. Hyaluronidase, which generates low molecular weight HA (LMW-HA), is induced in VSMC in a NADPH oxidase-dependent manner and LMW-HA stimulated ROS generation and cell proliferation in wild-type but not p47(phox-/-) VSMC, effects that were enhanced by thrombin pretreatment. Haptotactic VSMC migration toward HA was increased by thrombin in a CD44-dependent manner. HA expression in atherosclerotic lesions and plasma-soluble CD44 and HA levels were higher in apoE(-/-) compared with apoE(-/-)/p47(phox-/-) mice. HA-regulated pro-inflammatory gene expression was higher in apoE(-/-) than apoE(-/-)/p47(phox-/-) mouse aortas. GKT136901, a specific inhibitor of Nox1- and Nox4-containing NADPH oxidase activity, attenuated ROS generation and atherosclerosis and decreased CD44 and HA expression in atherosclerotic lesions. Together, these data suggest that increased CD44 and HA expression and CD44-HA-dependent gene regulation may play a role in atherosclerosis stimulated by NADPH oxidase activation.

CD44-deficiency on hematopoietic cells limits T-cell number but does not protect against atherogenesis in LDL receptor-deficient mice

OBJECTIVE

Vascular and inflammatory cells express adhesion molecule CD44. We demonstrated previously that enhanced CD44 localizes in human atherosclerotic lesions. Apolipoprotein E/cd44 double-deficient mice and apolipoprotein E-deficient mice transplanted with CD44-deficient bone marrow (BM) exhibit reduced atherosclerosis. Since CD44 is a novel factor in atherogenesis, it is imperative that it is investigated in more than one animal model to conclusively determine its role in this particular disease pathology. To test the hypothesis that CD44 expressed by hematopoietic cells plays a critical role in atherogenesis in the low density lipoprotein (LDL) receptor-deficient mouse model, we performed BM reconstitution experiments.

METHODS

Lethally irradiated LDL receptor-deficient mice were transplanted with either CD44-deficient or wild-type BM. Beginning 10 weeks after successful reconstitution, mice consumed a cholesterol-enriched atherogenic diet for 6 or 11 weeks.

RESULTS

Surprisingly, CD44-deficiency on BM-derived inflammatory cells did not affect lesion size. Additionally, neither group displayed differences in smooth muscle cell, macrophage, collagen, or elastin content as well as lipoprotein levels. However, lesions in CD44-deficient BM-recipient mice contained fewer T-cells compared to wild-type BM mice. Interestingly, CD44-deficient T-cells expressed less chemokine receptor-5 mRNA. Furthermore, in vivo leukocyte adhesion decreased in CD44-deficient mice compared to wild-type mice.

CONCLUSION

This study surprisingly revealed that atherogenesis does not require CD44 expression on hematopoietic cells in the LDL receptor-deficient mouse model. However, CD44 promotes T-cell recruitment, downregulates chemokine receptor-5, and participates critically in leukocyte adhesion in vivo. Consequently, the anti-atherogenic role of CD44 may require CD44-deficiency on cell types other than inflammatory cells in the LDL receptor-deficient mouse model.

Suppression of inflammatory signaling in monocytes from patients with coronary artery disease

Monocytes and T-cells play an important role in the development of atherosclerotic coronary artery disease (CAD). Transcriptome analysis of circulating mononuclear cells from carefully matched atherosclerotic and control patients will potentially provide insights into the pathophysiology of atherosclerosis and supply biomarkers for diagnostic purposes. From patients undergoing coronary angiography because of anginal symptoms, we carefully matched 18 patients with severe triple-vessel CAD to 13 control patients without angiographic signs of CAD. All patients were on statin and aspirin treatment. Elevated soluble-ICAM levels demonstrated increased vascular inflammation in atherosclerotic patients. RNA from circulating CD4+ T-cells, CD14+ monocytes, lipopolysaccharide-stimulated monocytes, and macrophages was subjected to genome-wide expression analysis. In CD14+ monocytes, few inflammatory genes were overexpressed in control patients, while atherosclerotic patients showed overexpression of a group of Krüppel-associated box - containing transcription factors involved in negative regulation of gene expression. These differences disappeared upon LPS-stimulation or differentiation towards macrophages. No consistent changes in T cell transcriptomes were detected. Large inter-individual variability prevented the use of single differentially expressed genes as biomarkers, while monocyte gene expression signature predicted patient status with an accuracy of 84%. In this comprehensive analysis of circulating cell transcriptomes in atherosclerotic CAD, cautious patient matching revealed only small differences in transcriptional activity in different mononuclear cell types. Only an indication of a negative feedback to inflammatory gene expression was detected in atherosclerotic patients. Transcriptome differences of circulating cells possibly play less of a role than hitherto thought in the individual patient's susceptibility to atherosclerotic CAD, when appropriately matched for clinical symptoms and medication taken.